Another cheap Marantz 2270 (this ones gonna be fun)

[goldswimmerb]

Hey guys, so figured I'd document my fun that I'm going to have with my recent acquisition of a "for parts" 2270 from ye olde evil bay site. According to the seller he started recapping it, then ran out of time to finish it, although my bet is that he messed up somewhere and gave up. Apparently the original issue was popping at high volumes which I would assume to be a faulty transistor somewhere (this model has no shortage of ones known to fail or go noisy)

Not sure why he went straight to a recap rather than replacing known trouble caused transistors first.

I know I'm in for a wild ride just looking at the work done so far. I'll be going through, checking his work and then making any modifications that are necessary, likely adding many of the upgrades from Lee's thread on the 2270.

So far my observations are:

The relay does not engage, have not checked DC offset yet so hoping it's just a fault in the relay circuit but you never know...

PSU:

Power supply looks pretty okay, don't have a picture but the solder work looked fine, a little light. Not a bad choice on caps here either though I usually go UPW here. I also would have swapped out the hot resistor and given it room to breathe.

Main Amp/Filter Caps:
He only got through one main amplifier, I'll be redoing this one for a number of reasons.

Panasonic main filters though, not bad

The wire work here is uh, well... Interesting to say the least. Will be redone. This channel also appears to have had it's outputs replaced at some point with Fairchild transistors, I'll probably be swapping all the outputs out for OnSemi while I'm at it.

Lastly I found the antenna wires to be cut, no clue why but doesn't give me confidence...

This is going to ba an adventure for sure, last guy in here probably didn't know much outside of capacitors.

Hoping I can save this one...

I'll be updating this thread as I find things and probably wind up asking for some help if there's anything really bizarre

 

[goldswimmerb]

Alright, so the relay isn't opening because of rail voltage on the side of the amp that was rebuilt. I'll be pulling the amp board at some point. Wish me luck, hoping it's just bad work but who knows.

 

[rBuckner]

Good luck then! Double check that the PS caps are in correctly. Maybe the outputs' insulators are just missing? Pretty please??

 

[goldswimmerb]

Good luck then! Double check that the PS caps are in correctly. Maybe the outputs' insulators are just missing? Pretty please??

Really hoping so, going to dig in deeper once:
I get this Marantz 2250B done
Get the Marantz 4300 up and running
And lastly get an Onkyo M-40 where someone butchered the relay board done

 

[goldswimmerb]

Good luck then! Double check that the PS caps are in correctly. Maybe the outputs' insulators are just missing? Pretty please??

This options would have been too easy.
Insulators are there, caps are oriented right from the looks of it.

Judging by the solder job (attached) I wouldn't be surprised if something was bridged.

 

[goldswimmerb]

One channel (the bad one) is using Fairchild outputs, I'll probably swap them back to Motorolas as I have a spare set.

Looking at the back of the board there's some interesting wires going places on the back of the board I don't remember from my last 2270.

Also noticed the seller has an orphaned dead 2270 amp for sale with Fairchild as well, wonder if they're related....

 

[goldswimmerb]

Got lucky here, was just a blown output transistor, had a nice CE short.

The amp board is cracked pretty bad on arrival, but as fixable with a wire to bridge the gap.

Old blown outputs:

Not sure if these Fairchild ones blew due to their ratings or blew from someone doing something terrible to this amplifier. Either way I got lucky and had a pair of the Original Motorolas left over from the previous 2270 I did.

Is it worth upgrading this one to MJ devices or are the Motorolas fine?

 

[goldswimmerb]

The new old transistors:

 

[ivandezande]

The Moto's should be fine.

 

[goldswimmerb]

As per AK and other suggestions I left the original outputs in there and used my spare motos for the bad channel. I do have some MJs on hand but think those may be best saved for another amp where I don't have the OEM transistors available.

Rebuilt the amp boards as per Leestereos suggestions, went with hFe matched KSA992s for the Differential pair. Didn't replace any other transistors since the drivers and predrivers seemed just fine. Also added flyback diodes to hopefully prevent a future blow out.

I was able to get the DC offset stable at 0MV +- .5mv since it does drift around a little bit as expected.

Probably going to do the preamp and phono pre amp next. Or the PSU since I think the last guy botched the relay circuit as there's a noticable pop on power off.

 

[rBuckner]

Glad you got it going. One worry from what I can see is that at the broken off corner it looks like there's a possibility of the standoff shorting to the board. Perhaps the standoff can just be removed. That or cut a piece of mylar or other plastic to go on the end of the standoff, then a 1/16" thick small diameter non-metallic spacer and a nylon washer that would capture the edge of the board.

I'd recommend the power supply board next and I agree that the popping issue is likely something on that board. Like someone just wired the contacts "on" all the time.

 

[goldswimmerb]

Glad you got it going. One worry from what I can see is that at the broken off corner it looks like there's a possibility of the standoff shorting to the board. Perhaps the standoff can just be removed. That or cut a piece of mylar or other plastic to go on the end of the standoff, then a 1/16" thick small diameter non-metallic spacer and a nylon washer that would capture the edge of the board.

I'd recommend the power supply board next and I agree that the popping issue is likely something on that board. Like someone just wired the contacts "on" all the time.

Definitely. Noticed the RC resistor was swapped too, may be a wrong value holding it open too long. I may see if I can just remove the standoff, or at least temporarily isolate it using electrical tape. Unfortunately that piece of board is long gone.

I had a 2252 with a pop on power down caused by the relay not closing soon enough as well (though that unit has a weird design where the power button is actually in circuit with the relay).

 

[rBuckner]

The 220uF timing cap often gets leaky enough in conjunction with the higher operating impedance (390K?) of that resistor to lengthen the timing. Sometimes to infinity (and beyond!!).

 

[goldswimmerb]

Rather than completing the PSU and relay board last night I decided to make my life a bit easier. The wires for the left amp board are impressively short on this one, making working a nightmare. I had some colored 20 gauge wire available so I decided to cut a few inches, solder that to the pins on the board and then connect the wires from the board to those from the Amp. Makes things 100x easier to work on.

I also removed the standoff from the broken board as to make sure that I didn't risk a short.

I started on the PSU, replacing the 5 diodes with UF4004s, and replacing the 5w 150 ohm resistor with a 7w Wirewound, I also lifted it up from the board a good bit to allow for cooling since it runs fairly hot.

Probably going to swap out the ELNAs the last guy threw in in favor of the upgrades Lee made on his.

 

[goldswimmerb]

I actually just got the PSU done as well, upped the relay delay a bit to allow for more settling time.

Working great. Will do preamp tomorrow probably.

I do have one issue, I noticed that the FM tuning meter is not functioning properly, the voltages across it seem to be correct (I think) however the needle just seems to be dragging or stuck. Is there an easy way to get to the meter to either lube it or replace it? Don't want to have to restring the tuner

 

[rBuckner]

I've met with failure most times when trying to dink with the innards of meters. There's no lubing them. If the needle is hitting the inner face you can likely do a gentle rebend and cure it. Used ones are always on eBay. I use seller Steve Galgiani in Sacramento quite a bit and have never had issues. He's quick to ship and great to deal with. No, we're not related!!

 

[goldswimmerb]

I've met with failure most times when trying to dink with the innards of meters. There's no lubing them. If the needle is hitting the inner face you can likely do a gentle rebend and cure it. Used ones are always on eBay. I use seller Steve Galgiani in Sacramento quite a bit and have never had issues. He's quick to ship and great to deal with. No, we're not related!!

So upon further testing the meter appears fine, I disconnected the Capacitor on the signal meter and it seems to work relatively normally but shifted over about 15-30 degrees to the right, the tuning needle that is.

 

[goldswimmerb]

It was at this point (the phono board) that I realized just how old this unit was. Haven't seen an epoxy diode outside of the VD1212 in some time.

Anyway, got the phono board done, noticed that this one is missing C716 and C717 from the factory. Any experts able to weigh in on the possible effects of this, or if I should add them?

Before:

After:

Would have used larger sizes WIMAs for looks but these work just fine. Upped the main DC filter here to 220UF (UPW), all other caps were replaced as per Leestereos guide. Replaced the tranistors with 4x KSC1815 and 2x KSC1845, diodes became 1N4148s, and the VD1212 became 2x VD1212 diodes

 

[Super Noob]

https://audiokarma.org/forums/index.php?threads/project-marantz-2270.875252/

Just in case you didn’t see my rebuild. Used Lee’s build as my base line as well.

Nice Work!